1. Field of the Invention
The present invention relates to a programmable mask adapted for fabricating a biomolecule array and a method for fabricating a biomolecule array using the same, more particularly, to a programmable mask adapted for fabricating the biomolecule array such as DNA by illuminating ultraviolet light to a specific cell and a method for fabricating a biomolecule array using the same.
2. Description of the Prior Art
First, in a biomolecule or a macromolecule array formed on a substrate, the area composed of a kind of the biomolecule or the macromolecule is referred as a cell.
The research for the operation for performing the plurality of experiment at once by using the biomolecule or macromolecule array has been progressed. As the biomolecule or macromolecule array, there are, for example, polypeptide, carbohydrate, and nucleic acid (DNA, RNA) arrays. The most important thing in the research is to fabricate an inexpensive array having high density on the substrate, effectively.
At the present time, as the method for fabricating the biomolecule or macromolecule array, there are a spotting method for dropping a biochemical material to a desired location by moving a micro-robot in three dimensions, a photolithography method for selectively illuminating light to the desired location to vary the surface thereof so that the coupling reaction between the surface and the biomolecule is generated in only a specific location, and an electric addressing method for adjusting the electrode voltage of a microelectrode array to attach the biomolecule to only a specific electrode.
The spotting method includes a contact printing method for adhering a solution on a paper like as a seal is affixed and a non-contact printing method for dropping the solution. The contact printing method is progressed in order of a loading step, a printing step, and a washing step, by using a XYZ robot. Since this method uses a pin the end of which is formed with a groove like the point of a fountain pen, the volume of the sample can be reproducibly adjusted and a plurality of printing steps can be performed when the sample is loaded one time. However, this method has a demerit which the number of the arrays per the unit area can be not increased. As the non-contact printing method, there are a dispensing method and an ink-jet printing method. The dispensing method is the method for dropping the solution like as a micropipette is used, and the ink-jet printing method is the method which a fine pressure is applied to a reservoir such that the solution blows off. If the ink-jet printing method is used, the volume of the sample solution can be finely adjusted to nano-liter such that the number of the arrays per the unit area can be remarkably increased. In this method, every sample solution needs the reservoir, but the number of the reservoirs which can be provided to the robot is limited. Accordingly, this method can be used in only case where the array is fabricated by using only a few sample solutions.
Affymetrix corporation firstly use the photolithography method in a semiconductor manufacturing process (U.S. Pat. No. 5,959,098). When the ultraviolet light is selectively illuminated to the molecule immobilized to the surface of the substrate and having protecting groups by using a photomask, the protecting group falls out and OH group appears. When the solution including biomolecule or macromolecule monomer to be attached is dropped, the biomolecule or macromolecule monomer is fixed to only the portion in which the OH group appears. Since another protection group is present in this attached macromolecule monomer, another monomer can be attached when the light is selectively illuminated. Therefore, the biomolecule or macromolecule array having a desired array can be fabricated by repeatedly performing these operations. This method can fabricate the array having high density and synthesize in parallel. However, since a plurality of photomask are required, this method brings out a problem that it takes much time and cost. Accordingly, the method for fabricating the array by operating the micromirror of a micromirror array without using the photomask was developed (U.S. Pat. No. 6,271,957). This method brings out problems that the complex optical system is required and only a mosaic pattern can be obtained.
The electronic addressing method is the method for attaching the biomolecule by using the voltage controlling function of the microelectrode array, and includes a method for moving the biomolecule having a charge into electrode surface to generate physical or chemical coupling and a method for attaching the biomolecule within thin film when the thin film is formed by an electrochemical deposition (Cosnier, Serge, “Biomolecule immobilization on electrode surfaces by entrapment or attachment to electochemically polymerized films. A review” Biosensors & Bioelectronics 14: pp. 443-456 (1999)). For example, since the DNA has many a negative charge, DNA moves toward the electrode if the electrode has positive charges. At this time, if the physical or chemical coupling between the DNA and the electrode is generated, the DNA is attached to the electrode (U.S. Pat. No. 5,605,662). Such electrode addressing method brings out problems that it can be not applied to the case where a number of arrays are used and a microelectrode array is required. In addition, a method for electrochemically changing pH around the electrode to attach the biomolecule to the selected location was developed, and Combimatrix corporation discloses a method for combining an oligonucleotide to the selected location of the microelectrode by using this concept (U.S. Pat. No. 6,090,302). However, in this method, there is a problem that the yield of each reaction is low, thereby the degree of purity of each cell is low.
As the method for fabricating the biomolecule or macromolecule, a method using a LCD (liquid crystal display) type programmable mask which the transmission of the light can be adjusted without using the micromirror array was disclosed (U.S. Pat. No. 6,271,957, Korean Patent Publication No. 2001-2915). In the LCD type programmable mask, the operation for adjusting the transmission of the light in each pixel to generate optical reaction in the cell on the substrate is repeatedly performed, thereby the biomolecule or macromolecule array is fabricated. However, the LCD type programmable mask has problems in a point of view of polarization, UV transmission, and deactivation due to ultraviolet light. Accordingly, the programmable mask satisfies the next facts.
First, since the light output from the general LCD is polarized and the protection group on the substrate generally exists therein without orientation, every protection group exist in a specific cell on the substrate can not be stripped by the light output from the LCD. Accordingly, in order to increase the reaction yield in fabricating the array, the device for changing the light output from the LCD to the non-polarized light is needed.
Second, in the general LCD, the light in range of the visible ray is transmitted, but, in order to strip the protection group, the ultraviolet light having wavelength of 330-400 nm is required. In case of an orientation film and a polarizer provided in the general LCD, since it is readily deactivated the deactivation due to the ultraviolet light, the orientation film and the polarizer which are not affected by the ultraviolet light must be used. Also, the orientation film and the polarizer whose the absorption of the ultraviolet light is low must be used.
Third, in case of the TFT-LCD type programmable mask, a light shield field (a black matrix) can prevent the transistor from be affected by the ultraviolet light, but an amorphous silicon transistor of the driving circuit can be affected by scattered ultraviolet light. This is the demerit of the conventional programmable mask. Also, since the amorphous silicon transistor has dark-conductivity higher than photo-conductivity by 106 times, it can not function as a switching element, thereby the arranged state of the liquid crystal can not be adjusted.
Fourth, in order to strip the protection group in synthesis of the DNA, the suitable illumination dose of the light is required. In necessary, the synthesis must be performed, changing the wavelength of a small dose of the light. Since the illumination dose of the light depends on the intensity of the light source, the illuminated time of the light, the transmissivity of the LCD type programmable mask, the illumination dose of the light must be adjusted by electrically adjusting the transmission of the programmable mask.
Fifth, if the ultraviolet light is illuminated to the biomolecule, the reaction or the deactivation therein may be generated. In order to prevent this, only the ultraviolet light having a narrow wavelength range which can strip the protection group without affecting the biomolecule must be illuminated to the cell.
Sixth, in order to maximize the number of the cells per the unit area to fabricate the biomolecule array having high density, the number of the pixels in the LCD must be minimized. In order to reduce the size of the pixel, the LCD with a built-in driving circuit must be manufactured.
As mentioned above, in order to fabricate the biomolecule or the macromolecule array, the LCD type programmable mask which can solve the above-mentioned problems is required.